The entire disclosure of Japanese Patent Application No. 2008-007665, filed Jan. 17, 2008 is incorporated by reference herein.
The entire disclosure of Japanese Patent Application No. 2008-332954, filed Dec. 26, 2008 is incorporated by reference herein.
1. Technical Field
The present invention relates to a liquid jet head and a liquid jet apparatus ejecting liquid droplets from nozzles, and particularly to an ink jet print head and an ink jet printing apparatus ejecting ink droplets as liquid droplets.
2. Related Art
As an ink jet print head which is a representative example of a liquid jet head, there is known an ink jet print head which includes a passage forming substrate provided with pressure generating chambers for communicating with nozzles and piezoelectric elements on one surface of the passage forming substrate and in which a silicon substrate with a crystal face orientation of a (110) plane is used as the passage forming substrate and pressure generating chambers are formed by performing anisotropic etching (wet etching) on the passage forming substrate formed of the silicon substrate.
In the ink jet print head having the above-described configuration, the pressure generating chambers each have first and second (111) planes perpendicular to the (110) plane as the silicon substrate so as to be formed in a substantially parallelogram opening shape. As for the pressure generating chamber having this opening shape, ends of lower and upper electrodes included in a piezoelectric element are generally formed in a width direction (transverse direction) of the pressure generating chamber (for example, see JP-A-2007-098812).
In this configuration, the piezoelectric element extends in a longitudinal direction of the pressure generating chamber up to the outside of the pressure generating chamber, but the piezoelectric element is formed inside the pressure generating chamber in some cases. That is, the ends of lower and upper electrodes of the piezoelectric element are located inside the pressure generating chamber. In this configuration, when the ends of the lower and upper electrodes included in the piezoelectric element are formed in the width direction of the pressure generating chamber, a distance between the end of the pressure generating chamber in the longitudinal direction and the end of the piezoelectric element is not uniform in the width direction of the pressure generating chamber. For that reason, a displacement amount of a vibration plate by drive of the piezoelectric element in the end in the longitudinal direction of the pressure generating chamber is not uniform in the width direction of the pressure generating chamber. That is, the displacement amount of the vibration plate in accordance with drive of the piezoelectric element is increased, as the distance between the end of the pressure generating chamber in the longitudinal direction and the end of the piezoelectric element is longer. Accordingly, a problem may occur in that the vibration plate of the end in the longitudinal direction of the pressure generating chamber or the piezoelectric element is broken down (cracked) due to a difference in the displacement amount of the vibration plate.
This problem occurs not only in the ink jet print head ejecting ink droplets and but also in other liquid jet heads ejecting liquid droplets other than the ink droplets.
The invention is devised in view of the above-mentioned circumstance and an object of the invention is to provide a liquid jet head and a liquid jet apparatus capable of preventing a vibration plate or the like from being broken down due to drive of a piezoelectric element. In order to solve the above-mentioned problems, according to an aspect of the invention, there is provided a liquid jet head including: a passage forming substrate in which a pressure generating chamber being formed of a silicon substrate, in which a crystal face orientation of a surface is a (110) plane, and communicating with a nozzle ejecting liquid droplets; and a piezoelectric element which is formed above one surface of the passage forming substrate with a vibration plate interposed therebetween and each includes a lower electrode, a piezoelectric layer, and an upper electrode. In the pressure generating chamber, an end surface in a width direction thereof is formed of a first (111) plane perpendicular to the (110) plane and an end surface in a longitudinal direction thereof is formed of a second (111) plane inclined by a predetermined angle with respect to the first (111) plane. Ends of the lower electrode and the upper electrode in the longitudinal direction of the pressure generating chamber are located in a region opposite to between both ends in the longitudinal direction of the pressure generating chamber and formed in parallel to the end surface in the longitudinal direction of the pressure generating chamber. With such a configuration, a distance between the end in the longitudinal direction of the pressure generating chamber and the end of the piezoelectric element is uniform in the width direction of the piezoelectric element. Accordingly, it is possible to prevent the vibration plate or the like from being broken down in the end in the longitudinal direction of the pressure generating chamber.
Here, it is preferable that the piezoelectric layer extends from the end in the longitudinal direction of the pressure generating chamber to the outside of the pressure generating chamber and a lead electrode having an end connected to the upper electrode extends onto the piezoelectric layer to be drawn to the outside of the pressure generating chamber. With such a configuration, a displacement amount of the vibration plate in the end in the longitudinal direction of the pressure generating chamber is suppressed. Accordingly, it is possible to surely prevent the vibration plate from being broken down. Moreover, it is possible to scatter stress in the vibration plate.
It is preferable that the lower electrode and the upper electrode are patterned by dry etching. With such a configuration, the lower electrode and the upper electrode can be formed with high precision. Accordingly, it is possible to more surely prevent the vibration plate from being broken down.
It is preferable that the predetermined angle is an acute angle or an obtuse angle. In this way, when the predetermined angle formed between the first (111) plane and the second (111) plane of the pressure generating chamber is the acute angle or the obtuse angle, etching can be smoothly performed in correspondence with anisotropy of the silicon substrate. In addition, the length of the end (end side) of the second (111) plane contacting with the vibration plate can be set to be longer, compared to a case where the predetermined angle is a right angle. The end (end side) is a position where the piezoelectric element is displaced. When the length of the position is long, the stress applied per unit length is reduced. Accordingly, it is possible to obtain an advantage of improving a lift span of the vibration plate.
According to another aspect of the invention, there is provided a liquid jet apparatus including the liquid jet head described above. According to this aspect of the invention, it is possible to realize the liquid jet apparatus capable of improving reliability and durability.
10: PASSAGE FORMING SUBSTRATE
12: PRESSURE GENERATING CHAMBER
13: INK SUPPLY PASSAGE
14: COMMUNICATION PASSAGE
15: COMMUNICATION SECTION
20: NOZZLE PLATE
21: NOZZLE
30: PROTECTIVE SUBSTRATE
40: COMPLIANCE SUBSTRATE
50: ELASTIC FILM
55: INSULATING FILM
60: LOWER ELECTRODE FILM
70: PIEZOELECTRIC LAYER
80: UPPER ELECTRODE FILM
90: LEAD ELECTRODE
300: PIEZOELECTRIC ELEMENT